Keywords
dysembryoplastic - neuroepithelial - seizure
Introduction
The term dysembryoplastic neuroepithelial tumor (DNET) was first described in 1988
by Dauport et al[1] to describe a unique histological pattern of brain tumors associated with medically
intractable partial seizures which are surgically curable. Recent studies have found
surgical resection to be effective in seizure control in 98% of patients.[2] We report a 9-year-old male child presenting with recurrent partial seizures over
the past 6 months, which is uncontrolled on polytherapy. Complete resection was done,
following which patient was seizure-free at 6 months. Histopathology revealed the
tumor to be DNET.
This case is reported because of its rarity and ability to highlight the effect of
tumor removal on seizure control,particularly DNET.
Case Summary
A 9-year-old male patient presented with sudden onset of partial seizures for the
past 6 months. The patient experienced a total of five episodes. During each episode,
the patient engaged in irrelevant talk followed by deviation of mouth to left and
twitching movements. The episode lasted 5 minutes and there was no loss of consciousness.
There was no aura or tongue bite, but in the last episode, the patient lost consciousness.
There was no history of head trauma, high fever, vomiting, headache, and visual or
auditory symptoms. No history suggestive of motor weakness or sensory loss, cranial
nerve involvement, as well as no bladder or bowel complaints. The child was delivered
normally at full term and cried after birth, so no history to suggest birth asphyxia
or neonatal infection. Developmental milestones were normal. The child recorded average
scholastic performance.
On examination, the child was found to be consciously alert and interactive. There
was no focal neurological deficit or features of meningitis. No neurocutaneous markers
were seen. There was no papilledema.
The patient was started sequentially on phenytoin sodium, phenobarbitone, and clobazam
on weight-adjusted doses. However, seizures were still not controlled at 6 months.
Magnetic Resonance Imaging (MRI) of brain was done with and without contrast. MRI
revealed a lesion approximately 4.1 × 3.6 × 3.2 cm in the right medial temporal lobe.
It was hypointense to brain on T1 ([Fig. 1]) and fluid-attenuated inversion recovery (FLAIR), hyperintense on T2-weighted images
([Fig. 2]). Diffusion restriction was present and there was minimal contrast uptake ([Fig. 1]). There was no evidence of mass effect or midline shift.
Fig. 1 Preoperative T1 contrast magnetic resonance resonance imaging.
Fig. 2 Preoperative T2 and fluid-attenuated inversion recovery magnetic resonance resonance
imaging.
After discussing the risks and benefits with parents, the patient underwent preanesthetic
checkup and was also taken up for craniotomy and excision of tumor. A right frontotemporal
craniotomy was done in the supine position. Under microscopic view, gross total excision
was done. The tumor was located in the right temporal lobe posteriomedially. It was
greyish soft, moderately vascular, and suckable except at the periphery. After assuring
hemostasis dura was primarily closed and bone flap was replaced. The child was reversed
and intubated. There were no intra or postoperative complications or seizure episodes.
Postoperative computerized tomogram (CT) showed adequate decompression and no hematoma
formation ([Fig. 3]).
Fig. 3 Immediate postoperative computerized tomography scan.
The child was started orally on day 1 postoperatively and ambulated. There were no
further seizure episodes.
The patient was continued on phenytoin and clobazam, and phenobarbitone was tapered
gradually.
MRI at 3 months revealed no recurrence or residual tumor ([Fig. 4]
[5]). At 6 months, the child was doing well with no cognitive impairments. It was planned
to stop clobazam at the 1-year mark. The patient's parents were advised follow-up
every 3 months.
Fig. 4 Postoperative T1 contrast.
Fig. 5 Postoperative T2 magnetic resonance resonance imaging.
Histopathology on routine hematoxylin and eosin revealed multiple glial tissue bits,
showing a cellular tumor arranged in multinodular pattern and composed of round to
oval oligodendrocyte-like cells and axons ([Fig. 6A]). Interspersed were normal glial tissue and floating neurons ([Fig. 6C]). There were focal areas of mucoid-like matrix and microcystic change ([Fig. 6B]). Focal cortical dysplasia was also seen. On immunohistochemistry, isocitrate dehydrogenase
(IDH) was negative, glial fibrillary acidic protein (GFAP) was noncontributory, synaptophysin
and chromogranin was positive, and Ki67 labeling index was less than 1%. Cells were
positive for Neuronal Nuclei (NeuN) ([Fig. 6D]). These features were considered consistent with a pathological diagnosis of DNET.
Fig. 6 Histopathology. (A) Representative images from tumor tissue (H&E; 40x; arrow). (B) Microcytic areas (H&E; 100x; black arrow) and specific glioneuronal elements (H&E;
100x; red arrow). (C) Tumor containing oligodendrocyte-like cells in a mucoid background containing floating
neurons (H&E; 400x; arrows). (D) The neurons are immunopositive for NeuN(100x).
Discussion
DNET as a distinct pathological entity has been well-documented after its description
by Dauport et al.[1] They are usually seen in young adults, with the most common site of occurrence being
the temporal lobes, but they may also occur at other sites.[1]
[2]
[3]
[4]
Common clinical features include a history of partial seizures, with or without generalization,
onset before 20 years of age, and absence of neurologic deficit[3] Our patient's profile is consistent with these clinical criteria.
MRI is the investigation of choice. Commonly seen features are cortical location of
the lesion, cystic appearance, absence of mass effect or peritumoral edema. Other
features are calcification, absence of contrast enhancement, and scalloping of the
overlying cortical bone Differential diagnosis include low-grade glioma and ganglioglioma.
FLAIR and apparent diffusion coefficient (ADC) may be helpful in distinguishing them.[3]
[4]
Surgical resection of tumor is documented to be effective in long-term seizure control
in cases of DNET.[1]
[2] It has been also found that it is safe in terms of mortality as well as morbidity.
Lesionectomy, with or without additional resection, and use of brain mapping are the
available treatment options.[2] Recurrence is rare. In a review by Ranger and Diosy, they found surgical resection
effective in improving control in 98% of patients and long-term seizure freedom in
86%. They found no deaths (immediate or delayed). Recurrence was seen in two out of
185 patients Hence, it is of importance to recognize this rare entity where excellent
seizure control is possible with minimal morbidity and mortality.[2] In our patient, we were able to stop one of the three drugs (phenobarbitone) and
planned to stop clobazam subsequently.
Conclusion
DNET are rare tumors occurring early in life, presenting with intractable seizures.
Surgical resection offers a good and safe chance for long-term seizure control.
